Food patty-forming, or patty-molding, machines are described for example in U.S. Pat. Nos. 3,952,478; 4,054,967; 4,182,003; and 4,329,828, and PCT published applications WO 99/62344, and WO 2005/02766782 A2, herein incorporated by reference. The patty forming machines may be those commercialized by FORMAX Inc. of Mokena, Ill., including the F-26™, ULTRA26™, Maxum700®, F-19™, F400™, F-6™ patty forming machines.
In one type of food patty-forming machine a mold plate, having patty-shaped cavities, is reciprocated between a fill position and a knock out position. The cavities are located above or below a food product delivery apparatus. Within the food product delivery apparatus, the food product, such as ground beef or ground poultry, is pumped by a plunger through a manifold and then upwardly or downwardly through a fill slot and eventually into the mold cavities. When the mold plate is in the fill position, food product is delivered under pressure through the fill slot into the cavities, forming patties.
A breather plate is arranged above or below the mold plate. The breather plate includes breather holes that communicate or express air out of the mold cavities while food product is being filled into the cavities from below or above. The breather holes are typically located at a position with respect to the cavities being filled that is distant from the position of the fill slot, so that a uniform patty shape can be achieved as the air within the mold cavities and within the food product is expelled through the breather holes. During filling, the food product delivered through the fill slot advances through a transverse flow area defined by a width and height of the cavity, through the cavity toward the breather holes. After filling of the cavities, the mold plate is then shifted to the knock out position where the mold cavities are extended forward of the breather plate. The patties are then knocked out of the cavities by a knockout mechanism.
The present inventor recognizes that in addition to the food product material, air is pressurized within the mold cavity. This pressurized air expands in the part of the mold cavity that is first exposed to atmospheric pressure when the mold plate moves from a fill position to a knock out position. The expanding air may cause a lip to form on the portion of the patty.
The present inventor recognizes that it would be desirable to relieve pressurized air within formed patties before the mold cavity is exposed to atmospheric pressure. The present inventor recognizes that relieving pressurized air will reduce or eliminate any lip formation on a patty.